1. Field of the Invention
The present invention relates to lever-operated mechanisms for external prostheses. Certain embodiments relate to lever-operated mechanisms for a prosthetic system comprising a hard socket, for example, for a leg or arm prosthesis. Said lever-operated mechanisms may be used as a fastening mechanism to connect a hard socket to a liner for a residual limb, and/or as an air valve or other air-control passageway that is manually opened and closed, and/or other mechanisms that require a latch.
The preferred lever-operated mechanism is a lock system for connecting the distal end of a limb liner to the distal end of a hard socket. The lock is actuated by a lever system provided at or near the outer surface of the hard socket, wherein the lever may be easily swung to open and close the lock. When in the latched configuration, the preferred lock mechanism locks a liner pin into a bore in the hard socket, wherein the liner pin is an elongated pin assembly that protrudes downward from the distal end of the liner on the wearer's residual leg. When the wearer unlatches the preferred lock mechanism, with an easy and comfortable swing of the latch handle, the liner pin, and therefore, the liner and residual limb, are removable from the socket. Certain embodiments further have pressure-control features, such as adaptations for maintaining vacuum established inside the well of a hard socket in some suspension systems.
2. Related Art
Optimum connection/suspension methods for securing a prosthetic limb to a residual limb take into account several factors, including control, comfort, ease of donning and removal, and long term effects on the health of the skin and other tissue. These factors are weighed differently and influenced differently, depending on the wearer's residual limb, level of activity, and preferences. One reason that suspension solutions are not simple is that gravitational and other forces tend to cause separation between a prosthetic limb and a residual limb. This happens especially during the swing phase of the gait, when a prosthetic leg is additionally subjected to centrifugal forces. Patients have routinely worn a variety of belts, straps, cuffs and harnesses to prevent the prosthetic limb from separating from the residual limb, but such devices are inconvenient and tend to cause chafing against the patient's body, giving rise to sores and abrasions.
Advanced methods of suspension have been developed in recent years, for example distal lock mechanisms, proximal attachment systems, and “suction” and “vacuum” suspension. Examples of proximal attachment systems are those developed by the instant inventor(s) (Perkins, Coyote Design and Manufacturing, Inc., Boise, Ill., USA), illustrated in U.S. Pat. Nos. 6,666,894; 7,077,868; 7,431,738; and 7,850,739. Examples of distal locks are those developed by the instant inventor(s), illustrated in U.S. Pat. No. 6,334,876 (“876”), issued Jan. 1, 2002, wherein a liner pin is locked into the distal end of the hard socket (see FIG. 4). In the '876 Perkins distal lock device, a spring biases a plunger and an air-seal o-ring outward unless the wearer/assistant pushes the plunger radially inward.
Advanced, multiple-layer, roll-on liners (also called “second generation” liners) work in combination with the above advanced suspension methods. These liners comprise both a gel layer that lies against the skin to grip the residual limb, and a fabric layer contacts the hard socket but that does not seal against the socket as completely as a gel-only liner. These modern roll-on liners may be connected to the hard socket by proximal attachment systems and/or distal lock mechanisms, and/or may be urged/caused to remain in the hard socket by pressure differential between the well of the hard socket (below the limb) and the ambient atmosphere, hence, the use of the terms “suction” and “vacuum”. See the discussion of suction liners in Janusson, et al. (U.S. Pat. No. 6,706,364) and Janusson, et al. (U.S. Pat. No. 6,626,952).
Suction suspensions (more accurately described as “partial suction”, as discussed below) for modern roll-on liners typically utilize a pressure inside the distal end of the well of the hard socket that is on average moderately lower than ambient. Because the fabric layer does not provide a complete/absolute seal against the socket, some air leaks into the socket well typically from the top of the socket along the length of the liner. Suction suspensions typically do not utilize any pump or other mechanical device to pump air out of the well of the hard socket. Instead, for example, they utilize the force of the limb pressing into the socket combined with a one-way air expulsion valve adapted to open at a socket well pressure slightly above atmospheric, thus, lowering pressure inside the well to close to ambient pressure. Then, in the swing portion of the gait, the socket “tries” to pull away from the limb due to centrifugal forces, further lowering the pressure in the well to below atmospheric, thus establishing the “suction” condition in the socket. Therefore, in suction suspensions utilizing a multiple-layer liner, the socket well pressure may cycle slightly up above ambient pressure during at least some weight-bearing portions of the wearer's gait, but averages moderately below ambient, for example, in the range of ½-4.9 psi (and preferably 1-1.5 psi) lower than ambient. Such “partial suction” suspensions are more comfortable for many wearers than the “true suction fit” obtained with a gel-only liner.
“Vacuum” systems, on the other hand, utilize a vacuum pump or other mechanical device to remove air from the well, and may establish an air pressure inside the well in the range of about 1 psi below ambient to a much lower pressure approaching 14.7 psi below ambient. More typically, however, vacuum systems operate in a well pressure range lower than suction/partial-suction systems, for example at least 5 psi below ambient and even so low as to approach 14.7 psi below ambient.
In summary, therefore, a suction suspension (especially “partial suction”) is typically established and maintained by exhausting air from the distal end of the well when the user dons the socket and during each weight-bearing portion of the user's gait. Vacuum, on the other hand, is typically established and maintained by use of a vacuum pump connected to the well of the hard socket. Both suction and vacuum suspensions, however, typically are supplemented by mechanical connections between the limb liner and the socket, for example, distal locks that engage a protrusion/pin anchored to the distal end of a limb liner.
There is still a need for improved suspension systems for external prostheses, for example, improved mechanical devices that mechanically connect the limb liner to the socket and/or that help optimize control of pressure in the socket well. This is a need, for example, for improved distal lock systems that are easy to use and reliable. There is a need for an improved lock actuation system that is easy and reliable to use with one hand or one finger, which may be used on or with a variety of prostheses including those for legs and arms, and which may be adapted for vacuum, suction, or other attachment systems. Embodiments of the invention meet some or all these needs.